Blood cell analyzers for classifying and counting blood cells are provided with an automatic microscope, a means for taking an image of a cell that has been enlarged by the microscope, and an image processor for processing the obtained image and obtaining desired analysis information such as the number of blood cells of each classification (for example, refer to Japanese Laid-Open Patent Publication No. 7-20124).
The apparatus disclosed in Japanese Laid-Open Patent Publication No. 7-20124 is provided with a microscope for enlarging blood cells smeared on a slide glass, and a color television camera for taking the microscope image. The slide glass with the blood smear is installed on the stage of the microscope, the stage is displaced in the XY direction by the stage drive circuit to adjust the position of the slide glass on the stage. Furthermore, an objective lens is displaced vertically (Z-axis direction) by a focus drive circuit to adjust the focal position by auto focusing. The image from the microscope is taken by the color television camera, and the blood cell image is displayed on an RGB monitor.
Although this type of blood cell analyzer moves the stage to adjust the position of the slide glass, inertia may cause the stage to vibrate when the stage is stopped after positional adjustment. Then, when the auto focusing is performed prior to the attenuation of the stage vibration, the lens cannot be accurately focused on the specimen on the slide glass. Moreover, when imaging is executed before the vibration has attenuated, defocusing or image blurring occur in the obtained image. Therefore, in this type of conventional apparatus, the apparatus waits for a predetermined time until the vibration has attenuated after the stage has stopped, then auto focusing is executed and thereafter the enlarged image is obtained.
In conventional blood cell analyzers, however, sufficient waiting time must be ensured for the attenuation of the vibration in order to reliably attenuate stage vibration and take a clear enlarged image without blurring, thus slowing down the operation (processing speed) of the apparatus. In addition, since the vibration of the stage can not be detected, it is impossible to determine whether or not the vibration has attenuated, such that imaging may occur before the vibration has attenuated.